Recently, various apparatuses using light for the purpose of diagnosis and treatment of diseases are being developed. Particularly, various apparatuses for diagnosing diseases using skin autofluorescence emitting out of the skin by excitation light irradiated from a light source are being developed and used.
The autofluorescence is the emission of light from the skin after excitation light is absorbed into the skin. Since having the biometric data inside the skin, the autofluorescence serves as a biomarker of diseases, and enables checking of the damage of physiological state of all body organs by a non-invasive method.
For example, Advanced Glycation End-products (AGEs) are formed via glycoxidation of proteins in human body as a result of Maillard reaction which impairs the functioning of many proteins. In general, exposure to cardiac risk factors such as smoking, intake of high fatty acid containing foods, hypercholesterolemia, and oxidative stress due to acute diseases such as sepsis lead to generation of AGEs. Thus produced AGEs are slowly decomposed and accumulated over a long period of time in the body. An increase in AGEs production is associated with the progress of chronic diseases such as atherosclerosis. With the aging process, AGEs tend to accumulate in the body throughout a person's life.
During the continuation of hyperglycemia, continual reactions of non-enzymatic protein glycation and glycoxidation occur, and thus AGEs, i.e., a complex of irreversible glycogen and protein, are formed. Accumulation of AGEs rapidly progresses in patients suffering from diabetes, renal failure and cardiovascular diseases. AGEs are accumulated in various tissues including skin. AGEs have the characteristics of irradiating autofluorescence (AF) at a range of blue spectrum (peak near about 440 nm) by excitation light irradiation of the UV range (peak near about 370 nm)
AGEs can be used as a bio marker regarding a series of diseases, and enable to evaluate physiological damages of the whole body organs by measuring autofluorescence of skin using a non-invasive method. That is, AGEs can predict long-term complications in age-related diseases. In particular, the quantity of skin autofluorescence increases in patients suffering from diabetes and renal failure, and relates to the progress of vascular complications and Coronary Heart Disease (CHD). The AGE accumulation can be measured by skin autofluorescence by a non-invasive method, a non-invasive clinical tool useful for the risk evaluation of long-term vascular complications under environments associated with the accumulation of AGEs and diabetes.
US Patent Application Publication No. 2004-186363 (hereinafter, referred to as Reference 1) discloses technology of evaluating AGEs by measuring skin fluorescence near the forearm of a patient as a method and apparatus that are proposed for AGE evaluation using skin autofluorescence measurement.
In Reference 1, an excitation light source is a blacklight fluorescent tube that emits light in a UV wavelength range of about 300 nm to about 420 nm. The collection and recording of light are performed by an optical fiber spectrometer. In order to increase a measurement area, the end surface of an optical fiber is disposed apart from a transparent window of the apparatus by a certain distance (d is about 5 mm to about 9 mm). In order to reduce an influence of light reflected from skin, the optical fiber is disposed oblique to the surface of the window at about 45 degrees.
Specifically, in Reference 1, the end surface of the optical fiber for collecting light is disposed as distant as possible from a target spot. In this case, the area of the target spot to be measured is about 0.4 cm2.
However, there is a limitation in the above method that a fluorescent signal that is collected is considerably reduced as the measurement distance (d) increases to increase the measurement area of the target spot. Accordingly, in Reference 1 according to a related art, the reliability of data detection may be reduced due to a limitation of the size of the skin area that can be measured. Particularly, such an accuracy limitation is considerably represented in parts such as moles, vessels, and wounds that are heterogeneous spots of skin.
Meanwhile, US Patent Application Publication No. 2008-103373 (hereinafter, referred to as Reference 2) discloses an apparatus for measuring AGEs to perform a screen test of a diabetic. Similarly to Reference 1, the apparatus disclosed in Reference 2 includes an optical fiber spectrometer to perform fluorescence measurement on the forearm skin. However, unlike in Reference 1, optical fiber probes are provided in a form of bundle including multiple branches.
In the apparatus of Reference 2, UV light and blue light emitting from light-emitting diodes are irradiated on the forearm of a subject through optical fiber probes, and skin fluorescence and diffusion reflection light emitting therefrom are collected through the probes. The collected light is wavelength-dispersed in a spectrometer, and then detected by a linear array detector. Two branches (illumination fibers; channel 1 and channel 2) of the optical fiber probe serve to irradiate light on a target spot, and a third branch (collection fibers) delivers light from the target to a multi-channel spectrometer. The end surface of a tissue interface, where the branch bundles of the optical fiber probes are combined, becomes in contact with skin to be irradiated.
Light from a white light LED is emitted from one branch of the optical fiber probe for reflected light spectrum measurement, and light from an appropriate LED among LEDs emitting light of ultraviolet to a blue light spectrum range is emitted from another branch of the optical fiber probe via a switching apparatus. Various wavelengths can be selected to select optimal fluorescence excitation conditions. The reflected light spectrum measurement is used to detect autofluorescence generated due to melanin and hemoglobin and compensate for the measurement result. Respective optical fibers are disposed in the optical fiber bundle by a certain sequence. Optical fibers from three branches of the optical fiber bundle are sequentially disposed in a mosaic pattern at an interval of b=0.5 mm.
In Reference 2, since light is irradiated on the forearm of a subject through an optical fiber probe, the optical fiber probe is included as an optical-transmission medium.
However, the optical fiber probe has a limitation in delivery loss for each specific wavelength which occurs according to the medium characteristics of optical fibers. Further, additional optical design and optical system are required for incidence light generated from a light source based on a total reflection condition of optical fiber.
Additionally, since both apparatuses disclosed in References 1 and 2 include optical fibers in a light-receiving unit that receives light, there is an inherent limitation in the optical fiber probe of the light-receiving unit. Since References 1 and 2 are configured to use an optical fiber spectrometer and a linear array detector, there is a limitation in that the autofluorescence signal wavelength of AGE becomes relatively smaller in a detection area that is occupied by the linear array detector. Accordingly, a detected fluorescence signal is dispersed, and the light intensity of a wavelength to be detected by the linear array detector becomes relatively smaller. Also, due to the optical fiber probe and optical fiber spectrometer, it is difficult to minimize facilities.
On the other hand, the diagnosis apparatuses disclosed in References 1 and 2 have a limitation in that it is impossible to diagnose diseases such as a diabetic foot accompanied by diabetes.
The diabetic foot is a sort of serious complications that incur a diabetic foot ulcer and a lower leg amputation according to the progress of diabetes. It is reported that the diabetic foot occurs in about 15% of all patients with diabetes and about 40% to about 60% of all lower leg amputation patients are diabetic patients. The diabetic foot ulcer is a cause in about 80% or more of all lower leg amputation patients. About 90% or more of patients with the diabetic foot can be cured without amputation when they are appropriately treated at an early stage. The autofluorescence measurement test can be used for an early diagnosis of the diabetic foot. At an early stage of the diabetic foot, the diabetic foot usually occurs in one foot before its progress in the other foot. Accordingly, the early diagnosis of the diabetic foot using the fluorescence test can be performed by comparing and evaluating the fluorescence degree of skin of the symmetrical foot part. Therefore, for early diagnosis of diseases such as diabetic foot together with typical diabetes, there is a need for the development of an apparatus that enables a selective diagnosis on body parts to be measured.
Particularly, for implementing the selective diagnosis apparatus, the miniaturization and the mobility of the apparatus has to be first prepared. Accordingly, the efficiency of light irradiation and fluorescence detection in the apparatus is needed.
Meanwhile, although such a selective diagnosis is performed on body parts, the intensity of the fluorescence generated from the skin is affected by the light scattering and absorption occurring inside the skin as well as fluorescence substances included in the skin.
Therefore, it is very important to improve the efficiency of the light irradiation and the fluorescence detection and reduce a measurement error due to the light scattering and absorption inside the skin in order to achieve an exact diagnosis on selective diagnosis parts for more clearly discriminating between persons with diseases and persons without diseases.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.